An image printing method by an inkjet system is a method of allowing fine liquid droplets of ink to fly from an inkjet recording head, and allowing the droplets to adhere to a recording medium to be recorded, thereby performing printing. The inkjet system is advantageous in that the mechanism is relatively simple, the cost is low, and a high definition and high quality image can be formed.
Meanwhile, current fabric printing is performed by screen printing or the like. For such printing, it is necessary to prepare a plate copper for printing or a screen printing plate, before printing. Since it takes time and labor to prepare plates, and plates are very expensive, it is necessary to perform production in an excess of a certain amount, in order to collect the cost. For the purpose of small-scale production, production of a sample, or the like, a printing system without plate making is demanded.
In connection to the above, textile printing using an inkjet system, with which a dye can be supplied directly to a fabric, has been proposed. Inkjet textile printing is different from conventional textile printing, and is advantageous in that it is not necessary to prepare a plate, and an image having excellent gradation property can be formed quickly, and further, has merits in that delivery times may be shortened, answering to production of wide variety of products in small volume may be realized, a process of plate making is not needed, and the like. Moreover, since only an amount of ink necessary for image formation is used, inkjet textile printing is advantageous in terms of environment such that the volume of waste liquid is small as compared with the conventional methods.
In textile printing, the type of dye used is determined according to the type of fiber in fabric. For forming an image onto a fabric which is mainly composed of polyamide fiber such as silk, wool, or nylon, a method of using an acid dye has been proposed.
In general, the following properties are required with respect to the ink for inkjet textile printing.
(1) To form color with a sufficient density,
(2) to exhibit excellent color reproducibility,
(3) not to cause bleeding of formed image, or not to cause pollution of non-image area or other fabric, during the post-treatment process and/or laundering,
(4) not to cause clogging of nozzles of a recording head,
(5) not to cause change in physical properties (for example, viscosity) or precipitation of solids during storage of ink,
(6) to be able to carry out jetting stably without change in jetting properties, even after long-term storage, and
(7) that the formed image has excellent fastness (water resistance).
In regard to the task (1), generally, the concentration of dye in ink is heightened. However, a high-concentration dye ink may become high viscous due to evaporation of water, aqueous organic solvent, or the like from the nozzle tip, or a dye in a solid state may precipitate, whereby the problem (4) may be caused.
As a trial for obtaining high coloring force by using, as a colorant, an oxonol dye having a high molar absorption coefficient and excellent thermostability, a technique of enhancing the solubility of a dye having a specific structure and coloring a hydrophobic polymer substance by a printing method has been proposed (see, for example, Japanese Patent Application National Publication (JP-A) No. 2009-507083).
In regard to the task (2), study has been made in order to obtain stable color reproducibility, in the case of providing printed matters having the same pattern, by adjusting the hue of the dye used or physical properties of ink (see, for example, JP-A No. 2004-515657, and Japanese Patent Application Laid-Open (JP-A) Nos. 2007-203741 and 2009-227895).
In regard to the task (3), examination on improvement by adding a specific compound into ink has been conducted. However, when a colorant having an insufficient color optical density is used, the solids concentration in the ink is inevitably increased, and thus the task (5) and the task (6) are inevitable.
Improvement work by applying a specific pretreatment agent to fabric has also been carried out. For example, treatments of fabric by using a pretreatment liquid that contains a quaternary ammonium- or amino group-containing compound (see, for example JP-A No. H6-192976), a cationized starch (see, for example, JP-A No. H7-173780), an aqueous synthetic polymer compound (see, for example, JP-A No. 2010-163507), or the like have been proposed.
As a method for improvement in regard to the task (4), a method of using a specific aqueous solvent and the like has been proposed.
For example, a method of using trimethylolpropane or pentaethylene glycol as an aqueous organic solvent, and a method of adding a specific polyoxyethylene alkyl ether to ink have been proposed (see, for example, JP-A No. 2010-229251).
Application of a compound, which has a dissociable group and in which a metal is coordinated to the nitrogen atom of an azo bond, or a mixture thereof to textile printing use has been disclosed (see, for example, JP-A No. 2004-511610).